1. Field of the Invention
The present invention relates to an optical communication apparatus which is used as a system for transferring and detecting a light signal.
2. Description of the Related Art
Recently, an optical communication system which uses an optical fiber for planning a prevention of electromagnetic noise, an enlargement of has been put to a practical use, in place of the electrical communication system which transmits an electrical signal.
FIG. 6 is a configuration diagram showing a conventional optical communication apparatus which is used for such a system, and it is an optical communication system which, by turning a light emitting unit 1 electrically on/off, transmits this on/off information to a light receiving element 3 through an optical fiber 2. The light emitting unit 1 includes a light emitting element 1a composed of a LED and the like for converting an electrical signal to a light signal, a switch 1b for turning the light emitting element 1a on/off in response to information "1", "0", and a lens 1c for focusing an emission light of the light emitting element 1a to an end surface of the optical fiber 2, and an electrical switch is utilized as the switch 1b.
In the optical communication apparatus configured as above, when transmitting a light signal from one light emitting unit 1 to a plurality of light receiving elements 3 by time-dividing the light signal, the switch 1b should be switching in high speed. Also, when transmitting the light signal from a plurality of light emitting units 1 to the plurality of light receiving elements 3 with 1:1 ratio, the plurality of light emitting units 1 and the light receiving elements 3 which have selectivities for the wavelengths .lambda.1, . . . ,.lambda.n, are placed on the optical fiber 2 corresponding with 1:1 ratio, by wavelength multiplexing.
As the above described optical communication system, a system is known for monitoring the operations of a plurality of circuit breakers in a vending machine or a plant and the like, and the operations of a plurality of door switches in an automobile.
However, in the conventional optical communication apparatus as described above, because the light signal is generated by turning the light emitting element 1a on/off with the switch 1b in the light emitting unit 1 on the transmitting side, thereby there is a problem such that the lifetime of the light emitting element 1a is shortened, and reliability of the system is low. Also, because it is required to provide a power supply to the light emitting element 1a in the light emitting unit 1 on the transmitting side, it is necessary to install a power supply line other than the optical fiber 2, and it can not sufficiently make use of the merit of optical communication system such as the lightening of the system and the simplification of work, thereby there is a problem such that it is not applicable to an explosion-proof system.